Synthetic analogs of an Entamoeba histolytica glycolipid designed to combat intracellular Leishmania infection

Abstract

Intracellular pathogens belonging to the genus Leishmania have developed effective strategies that enable them to survive within host immune cells. Immunostimulatory compounds that counteract such immunological escape mechanisms represent promising treatment options for diseases. Here, we demonstrate that a lipopeptidephosphoglycan (LPPG) isolated from the membrane of a protozoan parasite, Entamoeba histolytica (Eh), shows considerable immunostimulatory effects targeted against Leishmania (L.) major, a representative species responsible for cutaneous leishmaniasis (CL). Treatment led to a marked reduction in the number of intracellular Leishmania parasites in vitro, and ameliorated CL in a mouse model. We next designed and synthesized analogs of the phosphatidylinositol anchors harbored by EhLPPG; two of these analogs reproduced the anti-leishmanial activity of the native compound by inducing production of pro-inflammatory cytokines. The use of such compounds, either alone or as a supportive option, might improve the currently unsatisfactory treatment of CL and other diseases caused by pathogen-manipulated immune responses.

Antileishmanial Effects of Synthetic Eh PIb Analogs Derived from the Entamoeba histolytica Lipopeptidephosphoglycan

“…We therefore examined the hemolytic activity and cytotoxicity of the synthetic compounds in vitro. Consistent with earlier results (20), ␣-GalCer and EhLPPG were weakly hemolytic, while the synthetic analogs showed minimal hemolytic activity and negligible cytotoxicity against human peripheral blood lymphocytes or murine splenocytes (Fig. 2).…”

“…In vitro activities of synthetic EhPIb analogs against L. major infection. We previously reported that EhLPPG and the first set of synthetic EhPI analogs reduced parasite loads in L. major-infected macrophages (20). Here, we tested the antileishmanial activity of the newly synthesized compounds Eh-1, Eh-2, Eh-3, Eh-4, Eh-5, and Eh-6 against L. major-infected bone marrow-derived macrophages (BMDMs) and human THP1 cells.…”

“…1a). EhPIb has a phosphatidylinositol scaffold, which has a long-chain fatty acid of either 30 monounsaturated carbons (C 30:1 ) or 28 saturated carbons (C 28:0 ), as well as an additional short-chain fatty acid (C 16:0 ) at the stereospecifically numbered 2-position (sn-2 carbon atom) of the myo-inositol moiety (20) (Fig. 1b).…”

“…Host targets for immunotherapy would ideally interfere with pathogen invasion, survival, and/or replication. We previously demonstrated that the immunostimulatory glycolipid EhLPPG and its synthetic analogs induce protective cytokine responses in immune cells as well as anti-parasitic effects in experimental in vitro and in vivo models of L. major infection (18,20). EhLPPG elicits its immunostimulatory effects via two mechanisms.…”

“…Simultaneously, CD1d-mediated presentation of EhLPPG by antigen-presenting cells (APCs) induces gamma interferon (IFN-␥) production by natural killer T (NKT) cells (18,19). A series of previously synthesized immunostimulatory compounds derived from the phosphatidylinositol (GPI) anchor of the native compound EhLPPG, EhIa and EhPIb, were found to exhibit antileishmanial activity in vitro and in vivo in a murine model of CL by inducing synthesis of proinflammatory cytokines (20).…”